Without a welded comp on a 10.5" you will require a Gear Head Works proprietary extension tube & Tailhook Mod 1. If you're set on the SBA3 you'll need a longer barrel. I have an 11.3" 5 56mm Ballistic Advantage Hanson barrel with A5 buffer system.
What caliber are you looking to build?
$770. No sales tax. Pick up in DE with low transfer fee or ship to NJ dealer for $36.
Beretta USA JX4922105 Cx4 Storm 9mm Luger 16.60" 10+1 Flat Dark Earth Flat Dark Earth Fixed Thumbhole Stock Flat Dark Earth Polymer Grip Right Hand